Saving lives with coatings

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Dora Hardy
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1 Saving lives with coatings The essentials of passive fire protection. Paul Mather. Passive fire protection by means of intumescent, cementitious or ceramifying coatings or layers has gained importance in recent years. What are the specific requirements on such systems? Passive fireproofing is the use of insulating systems designed to deter heat transfer from a fire to the structure being protected. These are generally coatings but also include insulating panels or blankets. In most cases passive fire protection materials are used in conjunction with "active" systems such as water sprays, sprinklers or inert gas suppression. In contrast to active fire protection systems PFP systems should be 'install and forget' solutions performing to the specified standard throughout the complete lifecycle of the structure, with minimal operational maintenance. The specification of a suitable PFP product for a project is usually based on a number of factors including fire type, duration, substrate material and type and environmental location. Fire test approval is one of the most important factors in assisting correct specification. A growing demand for passive fire protection Passive fire protection (PFP) systems are applied to structural building components (steel, concrete) to prevent the rapid heat transfer which would lead to early failure in case of a fire. PFP safeguards the structural strength of steelwork, the integrity of divisions and protects personnel and equipment for the duration of a fire or during escape. The collapse of the New York City World Trade Center towers, following the terrorist attacks of 11 September 2001, was the worst building disaster in recorded history, killing some 2,800 people. In response to this tragedy, the U.S. National Institute of Standards and Technology (NIST) conducted a three-year building and fire-safety investigation to study the factors contributing to the probable cause, or causes, of the post-impact collapse of the towers. The NIST expanded its research in high-priority areas such as fire resistive coatings for structural steel and issued a number of recommendations. Concerning PFPs, the NIST specifically recommended: "The procedures and practices used in the design of structures for fire resistance should be enhanced by requiring an objective that uncontrolled fires result in burnout without partial or global (total) collapse. Performance-based methods are an alternative to prescriptive design methods. This effort should include: (1) the development and evaluation of new fire resistive coating materials and technologies, and (2) the evaluation of the fire performance of conventional and high-performance structural materials (such as fire-resistant steels and concretes)." As a result of these recommendations, there is a growing demand for passive fire protection, particularly for materials that can be shop applied (offsite). This development is bringing onto the market new technologies which meet the changing needs of owners and contractors. The introduction of these unique products give savings to owners of buildings, contractors and applicators and, combined with improved aesthetics, are opening up new possibilities for specifiers, project designers and architects. Many types of fire need to be dealt with PFP products fall under specific performance categories, usually determined by the type of fire they are designed to withstand. These types of fire, often called fire loads, have a distinctive time/temperature relationship (except jet fires which have a specified fuel load) which is used to categorize the level of severity: Cellulosic fires Here the fuel is natural carbonaceous type materials such as wood and paper (Figure 1). These fires have relatively slow heat rise and a peak temperature of 950 C. Hydrocarbon fires This represents fires fuelled by oil spills or gas clouds, which are characterized by higher heat fluxes and faster attainment of a maximum temperature of 1100 C. After the Piper Alpha Platform fire in 1988, protection against hydrocarbon-fuelled fires has become the norm for the offshore industry. Jet fires A unique type of hydrocarbon fire caused by pressurized gases or fuels that are released through an orifice and then ignited. These produce even higher heat fluxes: peak temperatures can exceed 1200 C and generate highly erosive forces. Rapid rise fires These occur in a confined space and/or when the fuel is highly flammable, as in tunnel or nuclear fires. Testing PFP Products In every country, rules, regulations and building codes prescriptively specify the level of fire protection that is required for different structures: for example "60 minutes fire protection". However, there is a trend towards providing a level of protection commensurate with the risk and hazard involved - a "Fire Engineering" approach. The performance properties of a PFP product normally have to be assessed by a fire test, prior to certification. Such tests are defined by specific national and international standards. These provide a methodology for proving compliance with the fire resistance levels set for different fire types as set out in standard time/temperature curves (Table 1). Although fire test standards can be complex because of the sheer number available, more established ones like British Standards (BS), ASTM International, Underwriters Laboratories (UL) and the EN13381 European Standard are widely used internationally. Whether the fire resistance is defined by prescriptive regulation or by risk/hazard assessment, the level of resistance for structural steel will be defined as follows: - Fire type: cellulosic, hydrocarbon or jet fire - Fire duration: minutes or hours - Critical core temperature: typically between 400 C and 600 C for structural steel members - Unexposed (non-fire side) temperature: for divisions: typically 140 C Figure 2 shows the result of a typical simulation. The coatings used in this simulation were successful in delaying attainment of the critical level. Responsible specifiers and contractors only use products from manufacturers that are independently tested to the standards mentioned above. Of course, as with any certified product, the specifier should seek further details on the level of certification or additional certification which some architects or designers use such as UL263 exterior listing, approval for use in ISO environments or explosion testing to 4 bar overpressure. Furthermore, PFP for use in

2 buildings should have some level of hydrocarbon fire resistance (UL1709 Design XR627). Thin or thick films There are a wide range of PFP products available, including intumescent coatings and cement and fibre-based products, as both spray products and panels. Intumescent coatings are paints which react to form a thick char when exposed to a fire (Figure 3). To combat these different fire loads, PFP products can be split into two categories: - Category 1 - Cellulosic fire protection developed for use on civil construction and infrastructure projects. Intumescent coatings for this category are generally known as "thin film", with application thicknesses typically up to about 1mm. The material swells rapidly (intumesces) to up to 60 times the original thickness when exposed to fire. - Category 2 - Hydrocarbon, jet and rapid rise fire protection developed for high risk environments such as oil rigs and refineries. Intumescent coatings for this category are often labeled "thick film", with their thickness measured in millimetres rather than microns. The required coating can be anything from 3 to 20 mm thick, depending on the desired level of fire resistance. Off-site application of cellulosic PFP preferred Traditionally, intumescent coatings have been applied on site, but more recently, products have been developed which allow application off site or in shop. The NIST recommends the development of criteria, test methods, and standards, firstly, for the in-service performance of sprayed fire-resistive material used to protect structural components and secondly to ensure that these materials, as installed, conform to test conditions used to establish the fire resistance rating of components assemblies, and systems. Consequently, offsite application ensures a result, which is consistent and to specification. The main advantage of applying PFP offsite is that structural steel arrives at the place of use already fire protected. Should there be any fires on site before erection is fully complete, the steel will be fully protected. In many cases, when using a single coatings supplier, the steel should also arrive fully protected with a high performance PFP and paint system. The application of PFP offsite also greatly reduces complexity of a project by decreasing the number of workers present on site, helping with scheduling. Other advantages are: - Reduced cost - Steel is protected by companies operating in the most cost effective locations rather than conditions dictated by the site. - Easy access and large application areas lead to increased efficiency. - Reduced equipment and scaffold requirements on site. - No need to seal off areas during application or mask sensitive equipment. - Improved Quality Control - Controlled application conditions and auditable quality control procedures ensure that the correct thickness of PFP is applied. - Greater control over application techniques. - No access issues. - Environmental and Health & Safety impact reduced - With less people on the construction site the chance of accidents is reduced. - By eliminating the intumescent paint system on site there is a reduced chance of spills and fire. - The steel is at ground level, therefore there are no access issues. Performance testing is essential Passive Fire Protection manufacturers have to carry out extensive testing to demonstrate their products' properties by ensuring the coatings are correctly evaluated and meaningful performance data is established. Fire testing is essential to make sure that any PFP material specified or used meets the required performance standards for the structure set by national or international, legislation. In addition to their fire resistance, products are tested for suitability for use in different environments and for their ability not to deteriorate over time. To make sure the product sold matches the performance of the original, fire-tested material, recognised test establishments offer follow-up services to monitor factory quality control and undertake random product sampling and verification. By testing for any changes which may contradict their original certification of a product, these establishments ensure that the performance claims of PFP product continue to match actual performance in the field. However, it is worth noting that not all manufacturers subscribe to this service. A high quality PFP manufacturer will provide the user or specifier with: - the correct PFP product for the fire type scenario. - Recognised approvals. - An approved follow-up service. To meet these demands, Akzo Nobel's International Paint has developed a series of shop applicable intumescent PFP coatings which have recognised approvals for cellulosic fires (product name "Interchar") and hydrocarbon fires (product name "Chartek") Results at a glance - Passive fire protection systems help to overcome the catastrophic effects from fires in steel-structured buildings by prolonging their structural integrity and allowing for proper emergency response and evacuation. - The requirements and specifications for PFP coatings are very demanding. - Proper selection and qualification of a PFP coating requires intense cooperation between specifier, contractor and coatings manufacturer. - The coatings manufacturer has to provide both, specifier and contractor, not only with state-of-the-art PFP technology, but also with intensive support including pre-qualification and follow-up services. - Products properties have to meet the requirements of current trends in PFP application such as shop (off-site) application and increasing esthetic demands of architects and building owners. The author: -> Paul Mather is responsible for worldwide product development and technical support for Akzo Nobel's International Paint fire protection and insulation materials, where he is actively involved with the development of fire testing standards. Over the last 13 years he has written, or co-authored, a number of technical papers and articles concerning fire testing and fire protection issues.

3 Figure 1: Passive fire protection systems help to overcome the catastrophic effects from fires in steel-structured buildings by prolonging their structural integrity and allowing for proper emergency response and evacuation.

4 Figure 2: In this simulation the uncoated steel would fail in less than 20 minutes, whereas PFP protected steel hinders structural failure for more than 60 minutes.

5 Figure 3: In a fire, an intumescent coating reacts to form an insulating char which prevents rapid heat transfer to the steel structure.

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Passive protection against hydrocarbon hazards

PPG PITT-CHAR XP Passive protection against hydrocarbon hazards Our pioneering flexible intumescent technology saves lives and protects assets in the world s toughest fire and cryogenic environments. PPG